The new version of OS X brings iOS features such as Notification Centre, Game Centre and AirPlay mirroring will now be a part of the Mac Applications such as Notes and Reminders, which will be familiar to iPhone and iPad users are also coming to OS X.

“The developer preview of Mountain Lion comes just seven months after the incredibly successful release of Lion and sets a rapid pace of development for the world’s most advanced personal computer operating system," said Phil Schiller, Apple's senior vice president of worldwide marketing, in a statement.

The biggest new feature is Gatekeeper, which lets you control the apps that run on your Mac. With Gatekeeper turned on, your Mac will run only apps downloaded from the Mac App Store or those from elsewhere that have "a unique Developer ID from Apple". For added security, users can choose to run only apps from the Mac App Store.

The new security features clearly nudge users towards the Mac App Store - and towards a more controlled application environment, similar to the iTunes App Store. However, Gatekeeper is optional, so users who prefer to run whatever apps they like can continue to do so.

As with iOS, Twitter has been integrated throughout Mountain Lion to make it easier to share links, photos and other content. Sharing to Flickr and Vimeo is also possible from several places within the new version of the OS but Facebook and YouTube remain notable omissions.

Mountain Lion extends the integration of iCloud, Apple's cloud storage service, further into OS X. When users start up a Mountain Lion computer for the first time they will have the option to sign in with their Apple ID and automatically set up iCloud, FaceTime, the iTunes Store and the Mac App Store.

In a statement, Apple said: "The new iCloud Documents pushes any changes to all your devices so documents are always up to date, and a new API helps developers make document-based apps work with iCloud."